Casting zinc alloy



Patented Feb. 6,1940

UNITED STATES PATENT OFFICE.

- CASTING ZINC ALLOY Arthur Burkhardt, Berlin-Lichterfeld'e, Germany,assignor to Georg Von Giesches Erben, Breslau, Germany, a corporation ofGermany No Drawing. Application October '7, 1938, Serial 4 Claims.

. l have described a zinc alloy to which plasticity,

i. e., good i'orging and extruding properties in cold condition, isimparted by providing a copper content of 2 to 8%, and by so determiningthe content of aluminium that it corresponds to the 10 proportion of 12to 22 parts of copper to 1 part of aluminium. In this manner, an alloyis obtained which possesses an unequalled constancy of dimensions.

It is an object of my present invention to provide a casting zinc alloyof constant dimensions.

As described in the said co-pending application, aluminium reduces andcopper increases the length of casting alloys of this kind. This is dueto the fact that casting alloys, as compared with cold-forged plasticalloys, do not possess a direciinnal structure or anisotropic texture,but conziSl. of irregularly distributed crystal grains. The changes inlength produced by the aluminium and the copper are quite different andof a vec- Lorial character. Another distinction as compared with thesaid plastic alloys is that changes of dimensions occur at a'difierentvelocity in plastic and in casting alloys.

Under these conditions, it was necessary to investigate properproportions for an alloy which possesses good casting properties, andconstant dimensions. v

I have found that such an alloy comprises copper from 1 to 10%,aluminium from about 0.05 to a about 0.6%, and zinc as the remainder,and that the copper and the aluminium must be proportioned at the rateof 1'? to 19 parts of copper and 1 part of aluminium.

Alloys'according to theinvention, in addition 40 to their good castingproperties, possess considerable strength and are particularly suitablefor gravity and pressure die casting. For instance, an alloy accordingto the invention possesses a tensile strength of over 27 kilogrammes persq. I millimeter, as compared with 13 to 17 kg./sq. mm.

in alloys with tin or lead as the base, and constant dimensions, inpressure-die cast condition. The remainder is zinc, preferably finezinc, i. e., zinc of a high degree of purity, not less than 50 99.99%.However, the remainder may also be fine zinc with additions andimpurities, for instance, with the addition of magnesium, as is usual insuch zinc alloys. It is understood, therei In Germany October 23, 1937fore, that the phrase the remainder being substantially all zinc isintended'to include fine zinc, particularly zinc of the aforesaid highdegree of purity, and zinc containing minor amounts of additions orimpurities which are usual in zinc alloys land do not influence thecasting and other properties of the alloy according to my invention.

The following table gives examples of alloys according tothe invention.In all cases, the balance is substantially zinc.

Alloy No. Copper, Aluminium,

percent percent 2 0. ill 3 0. 166 4 0. 222 5 0. 278 6 0. 333

The proportion of copper and aluminium is preferably 18 parts of copperto 1 part of aluminium, and the most favorable percentage of copper isabout 4%. The proportion of 18:1 and the content of 4% copper arepresent in alloy No. 3, and it has been found that this alloy,

'in addition to its other favorable properties,

being substantially all zinc; the copper and the aluminium beingproportioned at the rate of 17 to 19 parts of copper and 1 part ofaluminium.

2. A casting zinc alloy of constant dimensions, comprising copper from 1to 10%, aluminium from 4 about 0.05 to about 0.56%, and the remainderbeing substantially all zinc; the copper and the aluminium beingproportioned at the rate of 18 parts of copper to 1 part of aluminium.

3. A casting zinc alloy of constant dimensions, comprising copper at therate of about 4%, aluminium from about 0.21% to about 0.24%, and theremainder being substantially all zinc.

4. A casting zinc alloy of constant dimensions, comprising copper at therate of about 4%, alu- 5o minium at the rate of about 0.222%, and theremainder being substantially all zinc.

ARTHUR B.

